Osteoarthritis of the hip can lead to severe pain and viability. Total hip arthroplasty is a commonly performed procedure for "end stage" disease. We have previously shown that this procedure can be a relatively cost-effective approach in improving quality-adjusted life expectancy if it is considered when the patient's functional state is "limited only to little or none of the duties of usual occupation or self care". The purpose of the study is to refine a computer-assisted continuous-risk utility assessment procedure.